Add eventName and update event

[joeytakeda]

I think, after lots of work and discussion, eventName (and the new and improved event) are near ready for showtime 🎉 .

This PR should close #2382 and #2466 (with thanks to @djakacki , @skurzinz, @sydb, and @JanelleJenstad !)

You can view the proposed version of the Guidelines here: https://www.sfu.ca/~takeda/tei-guidelines/issue_2382_eventName/html/

Major changes here include:

• The addition of <eventName>
• Significant changes to <event>s content model and description
• Changes to "13 Names, Dates, People, and Places"

For reviewers, if you can, please check the descs in event and eventName as some of will be outdated (or non-existent, in the case of eventName) (I'm also not sure if everyone assigned needs to review, but I thought that more eyes wouldn't hurt)

[sabineseifert]

(I suggested some changes but then hit the button just for "approve" not for requesting changes.)

[skurzinz]

Many thanks @sabineseifert @joeytakeda @sydb for revising this again. Sorry for being inresponsive, was traveling yet did check occasionally: every change was necessary and appropriate. Many thanks.

[ebeshero]

And, as I'm assigned, I'll merge it in now!